Single-cell Transcriptomics Reveals That the SORBS1/FBXO22/BAG3 Axis Drives Astrocyte Senescence Via Calcium Signaling and Affects Alzheimer's Disease-Related Neuronal Damage.

In Alzheimer's disease (AD), senescent astrocytes fuel neuroinflammation and neuronal damage via the senescence-associated secretory phenotype (SASP). Calcium signaling plays a crucial role in this process, but the underlying molecular mechanisms remain elusive. We retrieved scRNA-seq data from the Gene Expression Omnibus (GEO) for AD and control brains. After cell-type annotation, we resolved astrocyte sub-clusters. Pseudotime trajectory and differential-expression analyses identified SORBS1 as a key senescence-related gene, which we followed with gene-set enrichment analysis. Next, we established an in vitro AD model by treating astrocytes with amyloid-β (Aβ). We evaluated astrocyte senescence using SA-β-gal staining, qRT-PCR, Western blot (WB) for senescence markers, and ELISA for SASP cytokines. We measured concentration of Ca2+ with Fluo-4 AM probes. Subsequently, bioinformatic screening predicted FBXO22 as an interactor of SORBS1 and BAG3 as a ubiquitination substrate of FBXO22. We validated these interactions using Co-IP and in vitro ubiquitination assays. Finally, we constructed an astrocyte-neuron co-culture model. We detected neuronal cell viability, AChE activity, AD phenotype-related protein expression, apoptosis, and levels of inflammatory factors using MTT assay, specific kits, WB, flow cytometry, and ELISA, respectively, to assess neuronal damage. ScRNA-seq analysis revealed a marked reduction in astrocyte expression in AD brains, which may result from cellular senescence. The SASP gene SORBS1 was selectively up-regulated in astrocytes and significantly enriched in calcium-signaling pathways. Functional assays confirmed that SORBS1 accelerated astrocyte senescence. Mechanistically, SORBS1 interacted with FBXO22 to promote the ubiquitin-dependent degradation of BAG3, thereby amplifying calcium signaling, accelerating astrocyte senescence, and contributing to AD-related neuronal damage. We uncover a novel mechanism by which the SORBS1/FBXO22/BAG3 axis drives astrocyte senescence through the regulation of calcium signaling, thereby influencing AD-related neuronal damage. This finding provides a potential therapeutic target for AD treatment by targeting astrocyte senescence.